Comfort control system for space suit

ABSTRACT

A comfort control system for a space suit having cooling passageways therein for circulating coolant. A temperature sensor is placed on an uncooled area of skin of a person wearing a space suit and a thermal path of fixed conductance is provided between the temperature sensor and one cooling passageway whereby skin temperature is reduced as said person&#39;&#39;s metabolic rate increases.

ttes atent Starr [54] CCMHFUT CONTRUIL SYSTEM FUR SPACE SUM [72]Inventor: James B. Starr, St. Paul, Minn.

[73] Assignee: The United States oli America as represented by theSecretary of the Navy [22] Filed: Nov. 25, 1970 [2 1] Appl. N0.: 92,622

[52] US. Cl. ..165/32, 73/362 R, 73/3625, 73/3626, 73/340, 236/78 [51]lint. Cl. ..G05d 23/00 [58] li ielld oliSearch ..236/78; 73/362 R,362.5, 362.6, 73/340; 165/39, 32; 2/2.]

[56] References Cited UNITED STATES PATENTS 1,358,073 11/1920 Fulton"236 /10 1 Mar. 14,, 1972 2,208,267 7/1940 Ridge ..73/362.5X 3,367,3192/1968 Carter ..2/2.lR

Primary Examiner-Albert W. Davis, Jr. Attorney-R. S. Sciascia, H. H.Losche and Paul S. Collignon [57] ABSTRACT A comfort control system fora space suit having cooling passageways therein for circulating coolant.A temperature sensor is placed on an uncooled area. of skin of a personwearing a space suit and a thermal path of fixed conductance is providedbetween the temperature sensor and one cooling passageway whereby skintemperature is reduced as said persons metabolic rate increases.

2 Claims, 3 Drawing: Figures COOLANT TUBES WITHIN GARMENT PATENTEUMAR 14I972 COOLED UNCOOLED COOLED SKIN LAYER SENSOR if: T/ T HEAT FROM MUSCLELAYER ISOTHERMS SENSOR 3 /TEMPERATURE D 3: Lu COOLED-SKIN TEMPERATURELL] METABOLIC RATE FIG. 2

COOLANT T UBES WITHIN GARMENT INVENTOR JAMES B. STARR ATTORNEYSCROSS-REFERENCES TO RELATED APPLICATION Patent application of James B.Starr entitled, Temperature Sensor for Space Suit," Ser. No. 96,874,filed Dec. 10, 1970.

BACKGROUND OF THE INVENTION The present invention relates to aliquid-cooled garment and more particularly to a control system for aliquid-cooled garment for maintaining a comfortable thermal state forthe person wearing the garment.

The function of a control system for a liquid-cooled garment is tomaintain a comfortable thermal state for the person wearing the garment,and this function is automatic when the control system is able to sensesome index of the person s thermal state and then modulate thetemperature of cooling water flowing through passageway in said garmentin response to changes in that index. A number of indexes can be used tomeasure the thermal state of a subject. For example, oxygen consumption,heat rate, and respiratory rate indicate, with varied degrees ofaccuracy, the rate of metabolic heat generation. While rectal,tympanic-membrane and skin temperatures indicate heat storage, skintemperature is considered the most practical index of a persons thermalstate in automatic temperature control systems for space suits.

Effectiveness of a control system for a space suit depends on thefunctional relationship between skin temperature and cooling-watertemperature. For example, in most closed-loop proportional systems,coolant temperature is varied inversely with changes in skin temperatureby a relatively high gain fac tor. The net effect of such systems is tomaintain skin temperature at a nearly constant value. Constant skintemperature, however, does not provide maximum comfort under allconditions. For example, investigations have indicated that means skintemperature of a person wearing a space suit should be reduced as hismetabolic rate increases in order to provide maximum comfort. Areduction of skin temperature with increasing metabolic rate isequivalent to keeping a persons body in a neutral thermal state, thatis, at a constant heat storage level. In order to maintain a comfortablethermal state, the control system should automatically reduce mean skintemperature as the persons metabolic rate increases. Depression of skintemperature as metabolic rate increases can be accomplished by keepingthe rate of cooling in the vicinity of the sensor at a level less thanthe mean cooling rate of the liquid-cooled garment.

SUMMARY OF THE INVENTION The present invention relates to a comfortcontrol system for a garment, such as a space suit, and includes atemperature sensor which is to be placed on a small, uncooled area ofskin. The difference between sensor temperature and cooled-skintemperature depends on the conductance of heat between the sensor andthe cooling tubes. This conductance level will vary with the proximityof the sensor to the cooling tubes. In order to control the differencebetween the temperature of the sensor and the cooled area of the skin, athermal path of a fixed conductance is provided between the coolingtubes and the temperature sensor.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a diagram showing heat flowthrough a layer of skin;

FIG. 2 is a graph showing a relationship between sensor temperature andcooled-skin temperature for changes in metabolic rate; and

FIG. 3 is a side view, partly in section, showing a'preferred embodimentof the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing,there is shown in FIG. 1 a diagram of heat flow from muscle layersthrough a skin layer 11. temperature sensor 112 IS placed on a small,uncooled area of skin 111 and, during exercise, heat is transferred fromthe muscle layers to the skin. The cooled area of the skin will be at alower temperature than that of the temperature sensor 12. The differencebetween the cooled area temperature and the uncooled area temperaturetends to increase with heat generated in the muscle layers beneath theskin. If the skin temperature sensor 112 is incorporatedl in a high-gainproportional-feedback loop, coolant temperature is automaticallymodulated to keep the temperature of sensor 12 at a nearly constantvalue. As shown in FIG. 2 of the drawing, the skin temperature beneathsensor 12 remaiins essentially constant while the temperature of thecooled area of the skin is reduced as heat rejection increases.

The difference between sensor temperature and cooled-skin temperaturedepends on the conductance of heat between the sensor 12 and coolingtubes 14 which have passageways for a coolant 15. This conductance levelwill vary with the proximity of the sensor 12 to the cooling tubes 14.In addition, however, variations in the vascular properties of the skinlayer will also affect the conductance level. Consequently, thedifference between the temperature of sensor 12 and the cooled area ofthe skin will be difficult to control if conductance is only by the skinlayer.

Referring now to FIG. 3 of the drawing, temperature sensor 12 is shownplaced on an uncooled area of skin layer 11. A copper wire 16 isconnected between one cooling tube 14 and sensor 12 and provides athermal path of a fixed conductance value between the cooling tube andsensor 12. This arrangement facilitates adjustment of the extent of skintemperature depression as metabolic rate increases, that is, the extentof skin temperature depression will vary inversely with the conductanceof the wire 16 that connects the sensor 12 to the cooling tube 14.

lclaim:

l. A comfort control system in a space suit having a plurality of tubeseach having a passageway for carrying coolant comprising,

a temperature sensor adaptable to be placed on an uncooled portion ofskin of a person wearing said space suit, and

a thermal path of fixed conductance connected between said temperaturesensor and one of said tubes whereby said temperature sensor provides anoutput signal for reducing said persons mean skin temperature as saidperson s metabolic rate increases.

2. A comfort control system in a space suit as set forth in claim Iwherein said thermal path of fixed conductance is copper wire.

1. A comfort control system in a space suit having a plurality of tubes each having a passageway for carrying coolant comprising, a temperature sensor adaptable to be placed on an uncooled portion of skin of a person wearing said space suit, and a thermal path of fixed conductance connected between said temperature sensor and one of said tubes whereby said temperature sensor provides an output signal for reducing said person''s mean skin temperature as said person''s metabolic rate increases.
 2. A comfort control system in a space suit as set forth in claim 1 wherein said thermal path of fixed conductance is copper wire. 